Method for manufacturing semiconductor device capable of improving manufacturing yield

ABSTRACT

In a method for manufacturing a semiconductor device, probe pads are formed simultaneously with formation of an intermediate conductive layer, and a test operation is performed upon the semiconductor device by placing probes on the probe pads. Then, post-stage processes are performed upon the semiconductor device in accordance with characteristics of the semiconductor device obtained by the test operation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a semiconductor device which is suitable for manufacturing a large number of kinds of products.

2. Description of the Related Art

In a prior art method for manufacturing a semiconductor device such as a MOS device (see JP-A-3-196655 & JP-A-3-268441), probe pads are formed simultaneously with formation of a lower aluminum wiring layer to complete a monitoring MOS element. Then, a test operation is performed by placing probes onto the probe pads upon the monitoring MOS element. This will be explained later in detail.

In the above-described prior art method, however, even when the test operation indicates that the monitoring MOS element has failed to save the post-stage processes of the device, the manufacturing yield is low.

In order to improve the manufacturing yield, it has been suggested that the probe pads be formed simultaneously with the formation of the gate electrode layer (see JP-A-1-194433, JP-A-1-201964 & JP-A-4-215451). Even in this case, after the test operation indicates that the monitoring MOS element has failed, the post-stage processes of the device are saved, which may increase the manufacturing yield. However, if such devices are scrapped, the manufacturing yield is still low.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of increasing the manufacturing yield.

According to the present invention, in a method for manufacturing a semiconductor device, probe pads are formed simultaneously with formation of an intermediate conductive layer, and a test operation is performed upon the semiconductor device by placing probes on the probe pads. Then, post-stage processes are performed upon the semiconductor device in accordance with characteristics of the semiconductor device obtained by the test operation.

Since the post-stage processes such as aluminum wiring processes are changed in accordance with the characteristics of the tested semiconductor device, a large number of kinds of products can be manufactured, which increases the manufacturing yield.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the description set forth below, as compared with the prior art, with reference to the accompanying drawings, wherein:

FIGS. 1A, 1B, 1C, 1D and 1E are cross-sectional views for explaining a prior art method for manufacturing a semiconductor device;

FIG. 2 is a plan view of the device of FIG. 1E;

FIGS. 3A, 3B and 3C are cross-sectional views for explaining a first embodiment of the method for manufacturing a semiconductor device according to the present invention;

FIG. 4 is a plan view of the device of FIG. 3C;

FIG. 5 is a flowchart for explaining the post-stage processes of the device (wafer or lot) manufactured by the method of FIGS. 3A, 3B and 3C;

FIG. 6 is a cross-sectional view for explaining a second embodiment of the method for manufacturing a semiconductor device according to the present invention; and

FIG. 7 is a plan view of the device of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the preferred embodiments, a prior art method for manufacturing a semiconductor device will be explained with reference to FIGS. 1A, 1B, 1C, 1D, 1E and 2 (see JP-A-3-196655 & JP-A-3-268441).

First, referring to FIG. 1A, a field silicon oxide layer 2 is grown by thermally oxidizing a P⁻-type monocrystalline silicon substrate 1 using a local oxidation of silicon (LOCOS) process. Then, the silicon substrate 1 is thermally oxidized to form a gate silicon oxide layer 3. Then, a polycrystalline silicon layer is deposited by a chemical vapor deposition (CVD) process, and then, the polycrystalline silicon layer is patterned by a photolithography and etching process to form a gate electrode layer 4. Then, N-type impurity ions such as arsenic ions are implanted into the silicon substrate 1 in self-alignment with the gate electrode layer 4 to form N⁺-type impurity diffusion regions 5. Then, a high temperature silicon oxide (HTO) layer 6, which has good step coverage characteristics, is deposited on the entire surface by a high temperature CVD process.

Next, referring to FIG. 1B, a tungsten silicide (WSi) layer is deposited on the entire surface by a sputtering process or the like, and the WSi layer is patterned by a photolithography and etching process to form a WSi layer 7. Note that the Wsi layer 7 serves as a ground layer or a power supply layer which is connected via contact holes (not shown) in the HTO layer 6 to the silicon substrate 1.

Next, referring to FIG. 1C, a boron-including phosphorus silicated glass (BPSG) layer 8 is deposited on the entire surface by a CVD process.

Next, referring to FIG. 1D, contact holes CONT are perforated in the BPSG layer 8, the HTO layer 6 and the gate silicon oxide layer 3 by a photolithography and etching process.

Finally, referring to FIG. 1E, an aluminum layer is deposited on the entire surface by a sputtering process, and the aluminum layer is patterned to form probe pads 9. Then, a silicon oxide nitride (SiON) layer is deposited on the entire surface by a CVD process, and the SiON layer is patterned by a photolithography and etching process to expose the probe pads 9.

FIG. 2 is a plan view of the device of FIG. 1E.

Thus, a monitoring MOS element is completed.

A test operation can be performed by placing probes onto the probe pads 9 upon the monitoring MOS element.

In the above-described prior art method, however, since the probe pads 9 are formed simultaneously with the formation of the aluminum layer which serves as a lower wiring layer, even when the test operation indicates that the monitoring MOS element has failed to save the post-stage processes of the device, the manufacturing yield is low.

In order to improve manufacturing yield, it has been suggested that the probe pads 9 be formed simultaneously with the formation of the gate electrode layer 4 (see JP-A-1-194433, JP-A-1-201964 and JP-A-4-215451). Even in this case, after the test operation indicates that the monitoring MOS element has failed, the post-stage processes of the device are saved, which may increase the manufacturing yield. However, if such devices are scrapped, the manufacturing yield is still low.

A first embodiment of the method for manufacturing a semiconductor device according to the present invention will now be explained with reference to FIGS. 3A, 3B, 3C, 4 and 5.

First, referring to FIG. 3A, in the same way as in FIG. 1A, a field silicon oxide layer 2 is grown by thermally oxidizing a P⁻-type monocrystalline silicon substrate 1 using a LOCOS process. Then, the silicon substrate 1 is thermally oxidized to form a gate silicon oxide layer 3. Then, a polycrystalline silicon layer is deposited by a CVD process, and then, the polycrystalline silicon layer is patterned by a photolithography and etching process to form a gate electrode layer 4. Then, N-type impurities ions such as arsenic ions are implanted into the silicon substrate 1 in self-alignment with the gate electrode layer 4 to form N⁺-type impurity diffusion regions 5. Then, an HTO layer 6, which has good step coverage characteristics, is deposited on the entire surface by a high temperature CVD process.

Next, referring to FIG. 3B, contact holes CONT are perforated in the HTO layer 6 and the gate silicon oxide layer 3 by a photolithography and etching process.

Finally, referring to FIG. 3C, a WSi layer is deposited on the entire surface by a sputtering process or the like, and the WSi layer is patterned by a photolithography and etching process to form WSi layers 7 a, 7 b, 7 c, and 7 d. Note that the WSi layer 7 d is not shown in FIG. 3C, but in FIG. 4. The WSi layer 7 a serves as a ground layer or a power supply layer which is connected via contact holes (not shown) in the HTO layer 6 to the silicon substrate 1. On the other hand, the WSi layers 7 b, 7 c and 7 d serve as probe pads.

FIG. 4 is a plan view of the device of FIG. 3C.

Thus, a monitoring MOS element is completed.

A test operation can be performed by placing probes onto the WSi layers (probe pads) 7 b, 7 c and 7 d upon the monitoring MOS element.

As illustrated in FIG. 5, after the above-mentioned test operation is carried out, the control proceeds to step 502 which determines whether the characteristics of the monitoring MOS element are higher than a first level α. Only if the characteristics of the monitoring MOS element are higher than the first level α, does the control proceed to step 503 in which lower and upper wiring layers made of aluminum having a relatively small circuit margin are formed at post stages to produce a product A. At step 502, if the characteristics of the MOS element is not higher than the first level α, the control proceeds to step 504.

At step 504, it is determined whether the characteristics of the monitoring MOS element are higher than a second level β(<α). Only if the characteristics of the monitoring MOS element are higher than the second level β, does the control proceed to step 505 in which lower and upper wiring layers made of aluminum having a relatively medium circuit margin are formed at post stages to produce a product B. At step 504, if the characteristics of the MOS element are not higher than the second level β, the control proceeds to step 506.

At step 506, it is determined whether the characteristics of the monitoring MOS element are higher than a third level γ(<β). Only if the characteristics of the monitoring MOS element are higher than the third level γ, does the control proceed to step 507 in which lower and upper wiring layers made of aluminum having a relatively large circuit margin are formed at post stages to produce a product C. At step 506, if the characteristics of the MOS element are not higher than the third level γ, the control proceeds to step 508, which scraps the wafer (or lot) including the monitoring MOS element.

Thus, various kinds of products can be produced in accordance with the characteristics of the monitoring MOS element, which increases the manufacturing yield.

In FIG. 6, which illustrates a second embodiment of the present invention, before the test operation, a BPSG layer 8 is deposited on the entire surface by a CVD process, and then contact holes CONT' are perforated in the BPSG layer 8 by a photolithography and etching process.

FIG. 7 is a plan view of the device of FIG. 6.

A test operation can be performed by placing probes onto the WSi layers (probe pads) 7 b, 7 c and 7 d through the contact holes CONT' upon the monitoring MOS element.

In the second embodiment, the characteristics of the monitoring MOS element can be determined in consideration of the affect of heat generated in a CVD process for depositing the BPSG layer 8, which could accurately determine the characteristics of the monitoring MOS transistor.

Also, in the second embodiment, the same aluminum wiring forming processes in the first embodiment as illustrated in FIG. 5 are carried out.

In the above-described embodiments, the layers 7 a, 7 b, 7 c and 7 d can be made of polycrystalline silicon by a CVD process instead of WSi.

As explained hereinabove, according to the present invention, since various kinds of products can be produced in accordance with the characteristics of the monitoring MOS element, the manufacturing yield can be increased. 

What is claimed is:
 1. A method for manufacturing a semiconductor device, comprising the steps of: forming probe pads simultaneously with formation of an intermediate conductive layer; performing a test operation upon said semiconductor device by placing probes on said probe pads; and performing post-stage processes upon said semiconductor device in accordance with characteristics of said semiconductor device obtained by said test operation.
 2. The method as set forth in claim 1, wherein said intermediate conductive layer comprises at least one of a ground layer and a power supply layer.
 3. The method as set forth in claim 1, wherein said probe pads and said intermediate conductive layer are made of tungsten silicide manufacturing by a same sputtering process step.
 4. The method as set forth in claim 1, wherein said probe pads and said intermediate conductive layer are made of polycrystalline silicon manufactured by a chemical vapor deposition process.
 5. The method as set forth in claim 1, wherein said post-stage process performing step comprises a step of forming aluminum wiring layers.
 6. The method as set forth in claim 5, wherein circuit margins of said aluminum wiring layers are changed in accordance with the characteristics of said semiconductor device.
 7. The method as set forth in claim 6, wherein the circuit margins of said aluminum layers are smaller when the characteristics of said semiconductor device are better. 